1. Field of the Invention
The present invention relates to a unit for controlling lens position in an optical pick-up device, and particularly, to a position control unit for lens of an optical pick-up device which is able to simplify the fabrication process and reduce the size and weight thereof by patterning a magnetic driving coil for focusing, tracking, and radial tilt driving of the lens on a printed circuit board (PCB).
2. Description of the Background Art
An optical pickup records and reproduces information such as video or audio data onto/from recording media, e.g., discs (or disks). A disc has a structure such that an information-recording surface is formed on a substrate.
Generally, an optical pickup device is installed on a CD player, etc. to radiate a laser light toward a recording media and to reproduce information recorded on the recording media by receiving light reflected from the recording media. And the optical pickup device comprises a hologram device for irradiating the light toward the recording media and changing the reflected light into an electric signal, a lens for concentrating the laser light irradiated from the hologram device on a disc, and a lens control unit for controlling location of the lens in order to compensate an error in case that an error is generated in the focus of laser light concentrated on the disc.
FIG. 1 is a perspective view showing a lens location control unit in an optical pickup device according to the conventional art, and FIG. 2 is a cross-sectional view showing a lens position control unit in the optical pickup device according to the conventional art.
In the lens position control unit in the conventional optical pickup device, a lens holder 106 on which a lens 104 is fixed is disposed on an upper surface of a suspended yoke plate 102, and suspension wires 108 are connected between the yoke plate 102 and the lens holder 106 to support the suspension of the lens holder 106.
The lens holder 106 includes a lens 104 fixed on a center part thereof, a focusing coil 110 for focusing/driving the lens holder 106 wound on an outer side thereof in a circumferential direction, and tracking coils 112 having (rough square shapes) for tracking/driving the lens holder 106 attached on front and rear surfaces thereof.
In addition, coil PCBs 114, to which the focusing coil 110 and the tracking coil 112 are electrically connected, are disposed on left and right side surfaces of the lens holder 106, and a plurality of suspension wires 108 are attached to the coil PCBs 114. Herein, two suspension wires 108 are respectively connected to each of the coil PCBs 114 to transmit a signal of a servo system to the focusing coil 110 and to the tracking coil 112, to support the lens holder 106 elastically, and to attenuate the shock from outer side from being transmitted to the lens holder 106.
Inner yoke 116 and an outer yoke 118 are disposed on front and rear side surfaces of the yoke plate 102 and facing each other with a predetermined interval therebetween. In addition, magnet 120 is attached to the outer yoke 118, and the focusing coil 110, and the tracking coil 112 are positioned between the inner yoke 116 and the outer yoke 118.
In addition, a yoke 124 for fixing a suspension PCB 122 which is connected to the suspension wire 108 is disposed on one side of the yoke plate 102 in a vertical direction, and a gel holder 128 in which damping gel 126 (having a high viscosity) is injected, is installed on the yoke 124 in order to attenuate vibrations of the suspension wires 108.
The suspension PCB 122 is connected to the PCB (not shown) of the main body through a flexible PCB or through a cable.
That is, the lens holder 106 having the lens 104 is lifted while maintaining a predetermined interval with the magnet 120 (which is attached to the outer yoke 118) by the elastic force of the suspension wires 108.
Operation of the lens position control unit in the conventional optical pickup device is described as follows:
When electric power is applied to the focusing coil 108 through the suspension wires 108 during the focusing/driving of the lens, the lens holder 106 is moved in a focusing direction, that is, in up-and-down direction to control the focus of a beam on an information-recording surface of the disc by an interaction between the focusing coil 110 and the flux generated on by the magnets 120. In addition, when electric power is applied to the tracking coil 112 through the suspension wires 108 during the tracking/driving of the lens, the lens holder 106 is moved in the tracking direction, that is, in left-and-right directions to control tracking of the beam on an information-recording surface of the disc by an interaction between the tracking coil 112 and flux generated by the magnet 120.
The conventional optical pickup device is able to reproduce only a particular kind of disc, and therefore, the need for an optical pickup device for a complex disc drive which is able to reproduce a disc for DVD and to record and reproduce a disc for CD-RW are developing.
In the optical pickup device of the combo type disc drive, a light source for DVD (650 nm wavelength) and a light source for CD-RW (780 nm wavelength) are used together using one lens.
A lens position control unit in the optical pickup device for the complex disc drive requires a focusing coil for focusing/driving of the lens, a tracking coil for tracking/driving of the lens, and a tilt coil for radial tilt driving of the lens.
That is, the lens position control unit according to the conventional art requires an additional tilt coil for radial tilt driving on the lens holder, and therefore, the size and weight of the optical pickup device is increased and fabrication processes thereof are complex.
Also, respective coils are formed by winding wire of a copper material, and the weight thereof is about one third of the entire weight of the lens position control unit. Therefore, the amount of electric current which is applied to respective coils is increased in order to control the position of the lens control unit, and a responding function is reduced.
Therefore, an object of the present invention is to provide a lens position control unit for an optical pickup device which is able to reduce the size of entire device, to reduce the weight of the device, and to simplify the fabrication process by patterning coils for focusing, tracking, and radial tilt driving of a lens on a printed circuit board (PCB).
To achieve the object of the present invention, as embodied and broadly described herein, there is provided a lens position control unit for an optical pickup device according to the present invention comprising: a lens holder, on which a lens is fixed, disposed on an upper part of a suspended yoke plate; suspension wires for supporting the suspension of the lens holder and applying electric power; coil PCBs, on which coils for focusing, tracking, and radial tilt driving of the lens holder are patterned, attached on front and rear parts of the lens holder respectively; and magnets positioned apart from the coil PCBs at a predetermined gap for driving the lens by an interaction with the coil PCBs.
The lens holder in the lens position control unit includes a lens on a center part thereof, mounting members to which the suspension wires are fixed on both side surfaces thereof, and a PCB for connecting electric power between the suspension wires and the coil PCB electrically attached thereto.
The PCBs for connecting electric power in the lens position control unit are attached to left and right side surfaces of the lens holder, and have suspension wires connected thereto respectively and electric power connecting patterns which are connected to the front and rear coil PCBs electrically.
Three suspension wires in the lens position control unit are connected to both PCBs for connecting electric power respectively.
The coil PCB of the lens position control unit comprises: a focus pattern for focus driving the lens holder; a tracking pattern for tracking/driving the lens holder; and a tilt pattern for tilt/driving the lens holder on which the lens is mounted toward the radial direction of the disc.
The focus pattern of the lens position control unit is formed to have long width in up-and-down direction on a center part of the coil PCB.
The tracking pattern of the lens position control unit is formed to have long widths in a side direction of the coil PCB on four corners of the coil PCB.
A pair of tilt patterns of the lens position control unit are disposed to face each other in a diagonal direction of the coil PCB edge, and formed to have longer widths in up-and-down direction of the coil PCB.
The tracking pattern and the tilt pattern in the lens position control unit are formed as lamination structures overlapping in a right angle direction with each other, and the tracking pattern is protruded toward the center portion of the coil PCB and the tilt pattern is protruded in up-and-down direction of the coil PCB centering around the overlapped portion.
The magnets in the lens position control unit are fixed inside of an outer core of the yoke plate, and comprise a first magnet which is disposed to face the focusing pattern and the tracking pattern and to interact therewith, and a second magnet which is disposed to face the tilt pattern and to interact with the tilt pattern.
The first magnet of the lens position control unit is disposed to form a North pole and a South pole in up-and-down direction of the coil PCB so as to be located facing the protruded part of the tracking pattern, and thereby the magnetic force can reach to focusing pattern and the tracking pattern.
The second magnet of the lens position control unit is disposed to cross with the first magnet at right angles so as to face the tilt pattern, and is formed to have a North pole and a South pole in left-and-right directions of the coil PCB.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.